Today, someone asked where the Venn Diagram was in Visio. There is a support article
The actual description for manually creating a Venn digram is okay, but a bit of overkill. You can just create a circle duplicate it twice, move them apart and distribute them horizontally (only worry about the distance between the first and third circle). Then select the middle circle and move it down. For a more precise positioning, create a square that would enclose the circles if position properly. Align the upper two circles with the top of the square and the bottom circle with the bottom.
Discard the square select the circles and fragment. (You will need Developer mode, Fragment is on the Devlopers part of the ribbon.) You can then colour the segments what ever colour you like.

Why not use tranaparency and blend? Though possible the result is muddy.

Then there is the Visio way.
Create three identical circles and a rectangle.
- Select the rectangle and the first circle. Align top and left.
- Select the rectangle and the second circle. Align top and right.
- Select the rectangle and the third circle. Align bottom and center.
- Delete the rectangle.
- Select the three circles and Fragment (on the Developer ribbon)
So, what is the size of the rectangle? The width should be between the diameter of the circle (overlap) to twice the diameter (no overlap). Since the centers of the three circles form an equilateral triangle when they are properly placed, the hieght should be 95.83% of the width.

John… Visio MVP in x-aisle
JohnVisioMVP.ca